Gas generating composition

ABSTRACT

A gas generating composition is obtained in which an amount of a combustion residue based on a unit amount of a gas generated is reduced.  
     A gas generating composition comprising nitroguanidine, guanidine nitrate or a mixture thereof as a fuel and further an oxidizing agent. The oxidizing agent is a perchloric acid salt, a nitric acid salt or a mixture thereof, and when the oxidizing agent is ammonium perchlorate, a chlorine neutralizer is further incorporated.

TECHNICAL FIELD TO WHICH THE INVENTION BELONGS

[0001] This invention relates to a gas generating composition which issuitable as a gas generating agent for an airbag system installed inautomobiles, airplanes and the like for protecting human bodies.

PRIOR ART

[0002] Various requirements have been put forth on a gas generatingagent for an air bag inflator. It is one of the requirements that acombustion residue after combustion should be reduced. When a combustionresidue generated by combustion of a gas generating agent is releasedoutside an inflator, there occur a first problem that a combustionresidue having a great heat capacity is contacted with an air bag tohole therethrough, a second problem that a large amount of a floatingmisty residue might cause an asthmatic passenger to have a fit, and athird problem that a large amount of a floating misty residue mightprevent a passengers' view to make accidents more serious. In order toprevent occurrence of such problems, it is required that a combustionresidue should be cooled and filtered through a coolant/filter to remainin an inflator. To this end, however, it is necessary to install a largecoolant/filter inside an inflator. In addition, when a large amount of acombustion residue is generated, a coolant/filter is likely to damage,and its function declines in a short time. Accordingly, for decreasingan amount of a combustion residue released outside an inflator, a methodof developing a gas generating agent in which an amount of a combustionresidue generated is substantially small is most desirable.

[0003] Further, it is currently required to more downsize an air baginflator and to reduce its weight more. However, an existing gasgenerating agent in which an amount of a combustion reside is largerequires an additional component such as a large filter for filtrationof a combustion residue or the like. It is therefore difficult to moredownsize an inflator itself. From this standpoint as well, a gasgenerating agent in which an amount of a combustion residue is decreasedhas been required.

DISCLOSURE OF THE INVENTION

[0004] This invention aims to provide a gas generating compositionhaving excellent combustion characteristics as a gas generating agent inwhich an amount of a combustion residue generated is decreased.

[0005] This invention further aims to provide an inflator system usingthe above gas generating composition.

[0006] This invention provides a gas generating composition comprising afuel made of nitroguanidine, guanidine nitrate or a mixture thereof andan oxidizing agent.

[0007] This invention further provides an inflator system using the gasgenerating composition.

[0008] The gas generating agent of this invention is, compared with gasgenerating agents disclosed so far, by far excellent because of thesmall amount of the combustion residue, whereby a gas generator can bedownsized more to be applied to an air bag system.

PREFERRED EMBODIMENT OR THE INVENTION

[0009] The fuel used in this invention is made of nitroguanidine,guanidine nitrate or a mixture thereof. A mixing ratio of nitroguanidineand guanidine nitrate is not particularly limited.

[0010] The content of the fuel in the gas generating composition varieswith types of an oxidizing agent, a chlorine neutralizer and a binderand an oxygen balance. It is preferably between 35 and 80% by weight,more preferably between 45 and 70% by weight.

[0011] Examples of the oxidizing agent used in this invention caninclude a perchloric acid salt, a nitric acid salt and a mixturethereof.

[0012] Examples of the perchloric acid salt and the nitric acid salt caninclude perchloric acid salts and nitric acid salts containing a cationselected from the group consisting of ammonium, alkali metals andalkaline earth metals. Examples of such perchloric acid salts and nitricacid salts can include ammonium perchlorate, sodium perchlorate,potassium perchlorate, magnesium perchlorate, barium perchlorate,ammonium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate,strontium nitrate and the like. Of these, sodium perchlorate, magnesiumperchlorate, sodium nitrate and mixtures thereof are especiallypreferable because the amount of the residue generated after combustionis small in particular.

[0013] As the oxidizing agent, the above-described compounds may becombined in any manner. However, the content of the oxidizing agent inthe gas generating agent is preferably between 65 and 20% by weight,more preferably between 50 and 25% by weight.

[0014] When ammonium perchlorate is incorporated as the oxidizing agent,a chlorine neutralizer is incorporated for neutralizing a chlorine-typegas such as hydrogen chloride, a chlorine gas or the like forstabilization.

[0015] As the chlorine neutralizer, a compound containing a cationselected from the group consisting of alkali metals and alkaline earthmetals can be proposed. As the compound containing such a cation, atleast one can be proposed which is selected from the group consisting ofcarbonic acid salts such as sodium carbonate, potassium carbonate,magnesium carbonate, calcium carbonate, strontium carbonate and thelike; nitric acid salts such as sodium nitrate, potassium nitrate,magnesium nitrate, calcium nitrate, strontium nitrate and the like;silicic acid salts such as sodium silicate, potassium silicate,magnesium silicate, calcium silicate, strontium silicate and the like;oxalic acid salts such as sodium oxalate, potassium oxalate, magnesiumoxalate, calcium oxalate, strontium oxalate and the like; oxides such asmagnesium oxide, calcium oxide, strontium oxide and the like; peroxidessuch as magnesium peroxide, calcium peroxide, strontium peroxide and thelike; cellulose salts such as sodium carboxymethyl cellulose and thelike; salts of tetrazole and triazole such as sodium salt, potassiumsalt, magnesium salt, calcium salt, strontium salt and the like of5-aminotetrazole; salts of bitetrazole such as sodium salt, potassiumsalt, magnesium salt, calcium salt, strontium salt and the like ofbitetrazole; and so forth.

[0016] The content of the chlorine neutralizer in the gas generatingcomposition is preferably between 5 and 40% by weight, more preferablybetween 10 and 30% by weight.

[0017] Further, the gas generating composition can contain, as required,a binder, a combustion catalyst and the like.

[0018] Examples of the binder can include inorganic binders such assilica, alumina, molybdenum disulfide, Japanese acid clay, talc,bentonite, diatomaceous earth, kaolin and the like; and organic binderssuch as metal salts of carboxymethyl cellulose and the like, starch,microcrystalline cellulose, guar gum, polyacrylamide, polyvinyl alcohol,stearic acid metal salts, oligomers and the like.

[0019] Examples of the combustion catalyst can include CuO, Cu₂O, Co₂O₃,CoO, Co₃O₄, Fe₂O₃, FeO, Fe₃O₄, MnO₂, Mn₂O₃, Mn₃O₄, NiO, ZnO, MoO₃,CoMoO₄, Bi₂MoO₆, Bi₂O₃ and the like.

[0020] It is advisable that the total amount of the additives in the gasgenerating composition is between 0.1 and 20% by weight.

[0021] In the gas generating composition of this invention, the gascomposition after combustion can be changed by changing an oxygenbalance. For example, it is possible to decrease CO (increase NOx) bychanging the oxygen balance to the plus side. Conversely, it is possibleto decrease NOx (increase CO) by changing the oxygen balance to theminus side. Accordingly, it is advisable to adjust the oxygen balance inconsideration of the safety to human bodies.

[0022] The gas generating composition of this invention can be producedby a dry method of mixing a fuel, an oxidizing agent, a chlorineneutralizer, additives and the like in a powdery state or a wet methodof mixing the same in the presence of water or an organic solvent.

[0023] Further, the gas generating composition of this invention canalso be molded into a desired form. For example, it can becompression-molded into a pellet using a pelletizer or into a disk usinga disk press machine, a pellet or a disk can be pulverized or granulatedusing a granulator to form granules or it can be extrusion-molded usingan extruder (extrusion-molding machine) to form an extruded pellet(non-perforated, single-perforated or porous shape).

[0024] These molding methods can be selected, as required, according toproperties and the like which are to be imparted to a molded article ofthe gas generating composition. For example, in the compression-moldingmethod, inherently, a binder is not required or may be used in a smallamount in the molding, so that this is suitable as a method of moldingthe gas generating composition of this invention. Further, when theextrusion-molding method is employed, it is easier to form an article ofa thin web than the compression-molding method. Accordingly, a moldedarticle of a thin web can be obtained with a composition having a lowburning rate. Further, the extrusion-molding method is suited formass-production because it is conducted for a relatively short period oftime. Still further, in case of a composition having a high burningrate, a size of a molded article can be increased, making it possible tomore improve a production efficiency. Besides, when theextrusion-molding method is employed, a molded article of anon-perforated, single-perforated or porous complicated shape can beproduced, so that various combustion characteristics can be imparted.

[0025] In the gas generating composition of this invention, the amountof the combustion residue per 1 mol of a gas generated is preferably 12g/mol or less, especially preferably 10 g/mol or less. This amount ofthe combustion residue is a total amount of components generated as asolid component and a liquid component in an inflator output temperaturewhich is calculated according to the formulation of the gas generatingcomposition.

[0026] The gas generating composition of this invention can be used inany device requiring a gas generating ability of a gun propellant or arocket propellant. It is especially suited for an inflator system of anair bag installed in automobiles, airplanes and the like for protectinghuman bodies.

[0027] The inflator system of this invention uses the above-describedgas generating composition, and they may be applied to a pyrotechnicinflator system, in which all the gas is supplied from a gas generatingagent, or a hybrid inflator system, in which gas is supplied from both acompressed gas such as argon and a gas generating agent.

[0028] A gas generating method of this invention is a method in whichthe above-described gas generating composition is burned as a fuel in agas generator, and it can be applied to various fields utilizing the gasgenerated by this burning. In the gas generating method of thisinvention, the gas generating composition is used as a fuel, making itpossible to decrease the amount of the combustion residue and improvethe gas output.

EXAMPLES

[0029] This invention is illustrated specifically with reference to thefollowing Examples and Comparative Examples. However, this invention isnot limited to these Examples only.

Examples 1 to 14 and Comparative Examples 1 to 3

[0030] Gas generating compositions having formulations shown in Table 1were obtained. An amount of a combustion residue generated when each ofthese gas generating compositions generated 1 mol of a gas was measured.The amount of the combustion residue of the gas generating agentcontaining nitroguanidine, guanidine nitrate or a mixture thereof wasshown as Examples, and an amount of a combustion residue measured bycalculation in gas generating agents disclosed in JP-A 9-501137, JP-A4-265292 and JP-A 6-239683 was shown as

Comparative Examples 1 to 3

[0031] The amount of the combustion residue in the gas generatingcompositions of this invention was much smaller than that in many gasgenerating agents disclosed to date.

Examples 15 to 28

[0032] Gas generating compositions having formulations shown in Table 2were obtained. An amount of a gas generated from these gas generatingcompositions was measured.

[0033] It was identified that in the gas generating compositions of thisinvention, the amount of the gas generated was sufficient for an airbag.

Examples 29 to 41

[0034] Gas generating compositions having formulations shown in Table 3were obtained. A burning rate of these gas generating compositions and adensity of strands of the gas generating agents were measured. Theburning rate was measured at a pressure of 70 kgf/cm².

[0035] It was identified that in the gas generating compositions of thisinvention, the burning rate was sufficient for an air bag.

Examples 42 to 52

[0036] Gas generating compositions having formulations shown in Table 4were obtained. These compositions were subjected to a test for a thermalstability. In the test for the thermal stability, the composition placedin an aluminum container was allowed to stand in a constant-temperaturebath of 105° C. for 400 hours, a weight loss ratio was found from thechange in weight of the composition before and after the test, and thethermal stability was evaluated.

[0037] The weight loss of the compositions of this invention was slight,and no change in the appearance was observed.

Examples 53 to 63

[0038] Gas generating compositions having formulations shown in Table 5were obtained. These compositions were subjected to a frictionsensitivity test and a drop hammer test. The test for the frictionsensitivity was conducted according to Standard ES-22 of the IndustrialExplosives Society, Japan using a BAM-type friction sensitivity tester.The test for the drop hammer sensitivity was conducted according toStandard ES-21 (1) of the Industrial Explosives Society, Japan using aniron hammer of 5 kg.

[0039] It was identified that both of the friction sensitivity and thedrop hammer sensitivity of the compositions in this invention were lowand the safety was high. TABLE 1 Amount of combustion residue based onamount Formulation wt. % of gas generated (g/mol) Example 1nitroguanidine/NaNO₃ (60.5/39.5) 8.2 Example 2 nitroguanidine/NaClO₄(63/37) 5.4 Example 3 nitroguanidine/Mg(ClO₄)₂ (65.1/34.9) 2.0 Example 4guanidine nitrate/NaNO₃ (64.2/35.8) 7.1 Example 5 guanidinenitrate/NaClO₄ (66.6/33.4) 4.8 Example 6 guanidine nitrate/Mg(ClO₄)₂(68.6/31.4) 1.6 Example 7 nitroguanidine/guanidine nitrate/NaClO₄(31.5/33.3/35.2) 5.1 Example 8 nitroguanidine/NH₄ClO₄/NaNO₃(56.2/25.4/18.4) 3.6 Example 9 guanidine nitrate/NH₄ClO₄/NaNO₃(60.1/23.1/16.8) 3.2 Example 10 nitroguanidine/NH₄ClO₄/Na₂CO₃ (56/25/19)5.7 Example 11 nitroguanidine/NH₄ClO₄/Na₂SiO₃ (55/25/20) 7.6 Example 12nitroguanidine/NH₄ClO₄/Na₂C₂O₄ (54/25/21) 5.2 Example 13nitroguanidine/NH₄ClO₄/CaO₂ (50/25/25) 7.2 Example 14nitroguanidine/NH₄ClO₄/NaNO₃/CMC-Na (47.1/26.6/19.3/7) 3.8 Comparative5-aminotetrazole/CuO (23.4/76.6) 44.5 Example 1 Comparative5-aminotetrazole/Sr(NO₃)₂/SiO₂ (33.1/58.9/8) 16.5 Example 2 Comparativecarbohydrazide/KClO₄/CaO (39/61/10) 14.2 Example 3

[0040] TABLE 2 Amount of gas generated Formulation wt. % (mol/100 g)Example 15 nitroguanidine/NaNO₃ (60.5/39.5) 2.9 Example 16nitroguanidine/NaClO₄ (63/37) 3.3 Example 17 nitroguanidine/Mg(ClO₄)₂(65.1/34.9) 3.3 Example 18 guanidine nitrate/NaNO₃ (64.2/35.8) 3.2Example 19 guanidine nitrate/NaClO₄ (66.6/33.4) 3.3 Example 20 guanidinenitrate/Mg(ClO₄)₂ (68.6/31.4) 3.5 Example 21 nitroguanidine/guanidinenitrate/NaClO₄ (31.5/33.3/35.2) 3.3 Example 22nitroguanidine/NH₄ClO₄/NaNO₃ (56.2/25.4/18.4) 3.5 Example 23 guanidinenitrate/NH₄ClO₄/NaNO₃ (60.1/23.1/16.8) 3.6 Example 24nitroguanidine/NH₄ClO₄/Na₂CO₃ (56/25/19) 3.5 Example 25nitroguanidine/NH₄ClO₄/Na₂SiO₃ (55/25/20) 3.2 Example 26nitroguanidine/NH₄ClO₄/Na₂C₂O₄ (54/25/21) 3.4 Example 27nitroguanidine/NH₄ClO₄/CaO₂ (50/25/25) 3.0 Example 28nitroguanidine/NH₄ClO₄/NaNO₃/CMC-Na (47.1/26.6/19.3/7) 3.5

[0041] TABLE 3 Burning rate Density Formulation wt. % (mm/sec) (g/cm³)Example 29 nitroguanidine/NaNO₃ (60.5/39.5) 11.8 1.74 Example 30nitroguanidine/KNO₃ (56.3/43.7) 32.9 1.72 Example 31nitroguanidine/Sr(NO₃)₂ (55.1/44.9) 7.7 1.90 Example 32nitroguanidine/NaClO₄ (63/37) 19.7 1.82 Example 33 nitroguanidine/KClO₄(60.1/39.9) 27.5 1.79 Example 34 nitroguanidine/Mg(ClO₄)₂ (65.1/34.9)7.4 1.65 Example 35 nitroguanidine/NH₄ClO₄/NaNO₃ (56.2/25.4/18.4) 16.21.72 Example 36 nitroguanidine/NH₄ClO₄/NaNO₃ (57/20.6/22.4) 17.2 1.72Example 37 guanidine nitrate/KNO₃ (60.1/39.9) 4.2 1.62 Example 38guanidine nitrate/NaClO₄ (66.6/33.4) 6.4 1.65 Example 39 guanidinenitrate/KClO₄ (63.8/36.2) 14.0 1.69 Example 40 guanidinenitrate/Mg(ClO₄)₂ (68.6/31.4) 3.6 1.54 Example 41 guanidinenitrate/NH₄ClO₄/NaNO₃ (60.1/23.1/16.8) 9.4 1.63

[0042] TABLE 4 Formulation wt. % Weight loss ratio (%) Example 42nitroguanidine/NaNO₃ (60.5/39.5) −0.11 Example 43 nitroguanidine/NaClO₄(63/37) −0.15 Example 44 nitroguanidine/Mg(ClO₄)₂ (65.1/34.9) −0.37Example 45 nitroguanidine/KClO₄ (60.1/39.9) −0.11 Example 46nitroguanidine/NH₄ClO₄/NaNO₃ (56.2/25.4/18.4) −0.11 Example 47 guanidinenitrate/NaClO₄ (66.6/33.4) −0.06 Example 48 guanidine nitrate/KClO₄(63.8/36.2) −0.07 Example 49 guanidine nitrate/KNO₃ (60.1/39.9) −0.07Example 50 guanidine nitrate/NH₄ClO₄/NaNO₃ (60.1/23.1/16.8) −0.06Example 51 nitroguanidine/NH₄ClO₄/Na₂CO₃ (56/25/19) −0.09 Example 52nitroguanidine/NH₄ClO₄/NaNO₃/CMC-Na (47.1/26.6/19.3/7) −0.09

[0043] TABLE 5 Drop Friction hammer sensitivity sensitivity Formulationwt. % (kgf) (cm) Example 53 nitroguanidine/NaNO₃ (60.5/39.5) >36  90-100Example 54 nitroguanidine/NaClO₄ (63/37) >36 40-50 Example 55nitroguanidine/Mg(ClO₄)₂ (65.1/34.9) >36 >100 Example 56nitroguanidine/KClO₄ (60.1/39.9) >36 30-40 Example 57nitroguanidine/NH₄ClO₄/NaNO₃ (56.2/25.4/18.4) >36 80-90 Example 58guanidine nitrate/NaClO₄ (66.6/33.4) >36 >100 Example 59 guanidinenitrarte/KClO₄ (63.8/36.2) >36 70-80 Example 60 guanidine nitrate/KNO₃(60.1/39.9) >36  90-100 Example 61 guanidine nitrate/NH₄ClO₄/NaNO₃(60.1/23.1/16.8) >36 80-90 Example 62 nitroguanidine/NH₄ClO₄/Na₂CO₃(56/25/19) >36 40-50 Example 63 nitroguanidine/NH₄ClO₄/NaNO₃/CMC-Na(47.1/26.6/19.3/7) >36 80-90

1. A gas generating composition comprising a fuel comprisingnitroguanidine, guanidine nitrate, or a mixture thereof, and anoxidizing agent comprising a perchlorate having an alkali metal oralkaline earth metal cation, a nitrate having an ammonium, alkali metal,or alkaline earth metal cation, or a mixture thereof.
 2. The gasgenerating composition of claim 1, further comprising a chlorineneutralizer.
 3. The gas generating composition of claim 2, wherein thechlorine neutralizer is a compound containing a cation selected from thegroup consisting of alkali metals and alkaline earth metals.
 4. The gasgenerating composition of claim 3, wherein the chlorine neutralizer is asilicic acid salt, an oxalic acid salt, an oxide, a peroxide, acellulose salt, a salt of tetrazole, a salt of triazole, or a salt ofbitetrazole
 5. The gas generating composition of claim 1, wherein thecontent of the fuel is between 35 and 80% by weight and the content ofthe oxidizing agent is between 65 and 20% by weight.
 6. The gasgenerating composition of claim 1, which further comprises a binder or acombustion catalyst as an additive.
 7. The gas generating composition ofclaim 1, wherein an amount of a combustion residue based on an amount ofa gas generated is 12 g/mol or less.
 8. An inflator system comprisingthe gas generating composition of claim
 1. 9. A gas generating methodusing a gas generated by burning a fuel, in which the gas generatingcomposition of claim 1 is used as a fuel to decrease an amount of acombustion residue and improve a gas output.